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NIH to Test Pneumococcal Vaccine in Older Adults

Scientists aim to elicit stronger immune response with higher dosage (Oct. 15)

In a study funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), researchers plan to see whether a higher dose of a pneumococcal vaccine will create a stronger immune response in older adults who received an earlier-generation vaccine against pneumonia and other pneumococcal diseases.

The study will compare two dosages of a pneumococcal vaccine approved for children aged 6 weeks to 5 years and for adults 50 years old and older. The trial will enroll up to 882 men and women aged 55 to 74 years.

The bacterium Streptococcus pneumoniae can cause a type of pneumonia called pneumococcal pneumonia. S. pneumoniae can infect the upper respiratory tract and spread to the lungs, blood, middle ear, or nervous system. Children younger than 5 years old and adults aged more than 65 years are most susceptible to becoming ill from pneumococcal pneumonia. Moreover, people who have been infected are susceptible to becoming re-infected.

For the past 30 years, the PPSV23 vaccine (23-valent pneumococcal polysaccharide vaccine) — known by the brand name Pneumovax 23 (Merck) — has been the standard protection from invasive pneumococcal disease in adults older than 65 years of age. While this vaccine protects against pneumococcal meningitis and bloodstream infections, it is unclear how well it protects against bacterial pneumococcal pneumonia. The newer PCV13 vaccine (13-valent pneumococcal conjugate vaccine) — known by the brand name Prevnar 13 (Pfizer) — protects against bacterial pneumonia and other invasive pneumococcal illnesses in children, but the vaccine’s efficacy and most effective dosage in adults are unknown. Earlier studies suggest that PCV13 may not induce as strong an immune response in older adults who previously received the PPSV23 vaccine within the past 5 years as in those who have not received the PPSV23 vaccine.

Researchers will conduct a phase IIb randomized clinical trial involving two groups of adults aged 55 to 74 years. The first group, consisting of 294 participants who have never been vaccinated with the PPSV23 vaccine, will receive a single 0.5-mL injection of the PCV13 vaccine. The second group, consisting of 588 participants who were vaccinated with the PPSV23 vaccine 3 to 7 years before study enrollment, will be randomized to receive one 0.5-mL injection of the PCV13 vaccine or 1.0 mL of the PCV13 vaccine administered as two 0.5-mL injections, one in each arm.

The researchers will evaluate the participants’ immune responses via blood samples drawn 28 days and 180 days after injection to compare responses between those who had been vaccinated with the PPSV23 vaccine and those who had not. The researchers will also ascertain whether the 1.0-mL dose of PCV13 is more immunogenic than the 0.5-mL dose in participants who were previously vaccinated with the PPSV23 vaccine.

Source: NIH, October 15, 2012.

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